<template>
  <div>
    <h1>App</h1>
    username:<input type="text" v-model="username">

    <input type="text" :value="username" @input="username = $event.target.value">
    {{ username }}

  </div>
</template>
<script setup>
import { ref } from 'vue';

const username = ref('jack');
</script>

<style>
div {
  border: solid;
  padding: 10px;
}
</style>